In recent years, a computer network using radio is widely used. Particularly in companies, a wireless LAN is widely used because an effort for installing wireline LAN cable or an effort for reinstalling wireless LAN cable due to layout change is not needed. In addition, a trend of using a wireless LAN as a public network service has appeared.
A physical layer or a MAC (medium access control) layer of a wireless LAN is standardized as IEEE802.11, and the standard is typically used in a wireless LAN of a company or a home.
In the wireless LAN, a range where a radio wave can reach is about 100 m, and accordingly, it is necessary to provide several wireless access points in order to cover a wide range of area. In addition, since the number of communication channels for performing wireless communication is limited and interference between communication channels may occur, it is necessary to make a study of an installation place so that the wireless communication is not affected between wireless access points or to set a channel where interference does not occur.
However, even if channels of wireless access points are assigned within a company and installation is properly made such that interference between the wireless access points does not occur, a radio wave from a wireless access point located in a department may reach a wireless access point located in another department, or a radio wave from another company may reach the company according to circumstances, a street being located between the company and another company. The radio waves from other wireless LANs have an adverse effect on wireless communication within a company, as interference waves.
Further, if a public wireless LAN service becomes popular and thus service providers install wireless access points at possible places, it is expected that a problem due to the radio wave interference will be more serious.
In the case of a wireless LAN, a range where a radio wave can reach in a wireless access point is limited. Accordingly, in order to perform wireless communication over a wide range that cannot be covered by one wireless access point, several wireless access points are generally provided such that communication ranges overlap one another to some degree so as to prevent a region where a radio wave does not reach from occurring.
In the related art, in the case when a plurality of access points exist, there has been proposed a method of selecting a wireless access point determined that the received signal strength is highest or a method of selecting a channel in which power of an interference wave is lowest.
On the other hand, in Non-patent Document 1, a method is proposed in which a weighting function corresponding to a communication throughput is calculated on the basis of equation 1 and then a wireless access point having a highest weighting function is selected.WSTA=(1−P)/N  (Equation 1)
Here, WSTA is a weighting function at the time of communication with a wireless access point, N is the number of wireless terminals connected with a wireless access point, and P is a packet error rate at the time of communication with a wireless access point.
However, in the method of selecting a wireless access point determined that the received signal strength is highest, interference is not considered. As a result, a probability that a communication error will occur increases if an interference source exists within a close range, which lowers the communication throughput.
Moreover, even in the method of selecting a channel in which the power of an interference wave is lowest, if a received radio wave of the selected wireless access point is weak, the probability that a communication error will occur increases, which also lowers the communication throughput.
Furthermore, in Non-patent Document 1, even though the method of selecting a wireless access point on the basis of the weighting function is proposed, it is not clear how to practically obtain the packet error rate before a wireless terminal is connected with a wireless access point so as to perform communication. In addition, Non-patent Document 1 does not disclose how to obtain the number of wireless terminals connected with the wireless access point.
[Non-patent Document 1] FUKUDA, Yutaka; ABE, Takamitsu; OIE, Yuji; “Decentralized Access Point Selection Architecture for Wireless LANs”, Wireless Telecommunications Symposium 2004, SA3, Pomona, Calif., USA, May 14-15 2004